Process for cracking oils



Aug. 23, 1932. H. A. FOUTS PRocEss FOR CRACKING oILs Filed May 2, 1928 2Sheets-Sheet l T0 CONDENSE? Aug. 23, 1932. H. A. FOUTS PROCESS FORCRACKING oms 2 Sheets-Sheet 2 Filed May 2, 1928 @www Patented Aug. 23,1932 UNITED STATES HORACE A. FOUTS, OF PORT TEXAS, ASSGNOR TOV'lI-IliTEXAS COMEAN, OF

NEW' YORK, N. Y., A CORPORATION OF DELAWARE v f rnocnss :son c nAcKINeoILs Applicationled May 2, 1928. Serial No. 274,379.

i This invention relates primarily to im- Y under considerableY pressurein a coil, from which the oil is delivered to a drum or a plurality ofdrums and the vapors generated in the process are sent through suitabledepvhlegmating or fractionating apparatus, such as a bubble tower or thelike, to separate the desired constituents, such as gasoline, from theheavier components which are condensed and recycled.v In most systemsVof this kindit is customary to force the oil through the coil in i theheating Zone from the top to the bottom of the latter, this being fromthe cooler to the hotter portions of the coil. The heavier constituentsof the generated vapors which are, f

as a rule, returned tothe coil for further cracking are generally mixedwith the fresh charge of oil before the latter is introduced into thecoil.

By the present invention it is proposed to handle the oil in an improvedmanner, which may here be briefly outlined. It is lirst contemplated toraise the temperature of the charge of fresh oil as far as possible byemployment of suitable heat exchangers through which the heat of theproducts resulting from the process, which` would otherwise be wasted,may be utilized. For this purpose it is proposed to passV the chargefirst through a heat exchanger, .whichV is suitably located in the vaporline above the fractionating tower. This arrangement not only providesfor the desired conservation of the heat in the generated vapors,vbutitalso serves to supply the desired cooling or regulating medium, in theform of refluxed'material, for the operation of the tower. After leavingthis heat exchanger, the fresh charge may be forced through a secondheat eX- changer, where it is adapted to receive additional heat fromthe tarryresidues drawn from the bottom of the drum, or battery ofdrums, employed inthe process. Upon leaving this second heat exchangerthe temperature of the oil will havev beenI 'i' raised to afconsiderable degree and the burden placed upon the primary heatingVunits will begreatly lessened. The charge is now preferably forcedthrough a ,suitabla economizercoil located in the path `of the hotgasses generated in thel main furnace which houses the main heatingcoil. From the outlet end of the economizer coil it is thenvcontemplated to pass the oil through a, section at the bottom or thehottest portion of the main heating coil. However, .at a point `justin.` advance of the inlet to Vthis lower. section of the heating coil,the fresh chargecof oil is preferably merged withal@ quantity of therefluXed material which is returned from the base of the bubble towerorother dephlegmator or fractionator. `The temperature of the twostreams of oil merged at this point will be substantially the same andit will be considerably less than the usual temperature of the oil atthe time it is sent through the hottest tubes of the heating coil. Uponleaving the lower section of this coil, the mixture of oil is preferablyintroduced into the top section of the main heating coil and is passeddownwardly through the latter 'to the progressively hotter sectionsuntil its temperature has been raised to the desired ipoint forintroduction into'one orr more of a series of drums or stills where arelatively large volume of oil is maintained at a cracking temperatureand under superatmospheric pressure. If desired, only one of these drumsor stills may be employed, al-

though it has been found preferable to lemploy a battery of three orfour of them. VExternal heat may be applied to the drums, if

desired, for the purpose of offsetting the heat losses, although this isnot essential4 and they may, if desired, be merely heatinsulated. f

According to the present invention, the

economiz-er unit and the main heating coil may,if desired, beconstructed and arrangedg'-, f'

as distinct units or they may constitute merely separate sections of onecontinuous coil so that the latter is in edect divided into threesectionsone the uppermost or coolest section, an intermediate section,and the,bot-.

lll

tom or hottest section. The coil in all of these sections may, ifdesired, be constructed in the form of one single, continuous passagethrough which all of the oil must be passed in series. However, it iscontemplated as preferable, in accordance with the present invention, toarrange and connect the'tubes, which serve to form the coil, in acombination parallel-and-series arrangement; for example, the uppersection, or economizer unit, may consist of groups of three tubes arraned in parallel and connected by suitable hea ers to place successivegroups of three tubes in series.

This will serve to provide three separate streams of oil inparallel'relation through the upper section where the intensity of theheat is not sov great and where the retarded movement thus brought aboutwill not be harmful but, on the other hand, will provide a greater timeperiodffor bringing the temperature of the fresh charge up to that ofthe refluXed condensate. Upon leaving the upper section, these threeseparate streams will preferably be merged by a suitable header into asingle stream for passing the fresh charge, as well as the refluXedmaterial subsequently joined with it, through the lower section of thecoil in which the tubes are preferably single-series connected. vThisarrangement will insure a very rapid flow of the oil through thelowermost tubes and will prevent to a large degree the deposition ofcarbon, which might otherwise result. The tubes constituting theintermediate section of the coil may,rif desired, be connected to formone single, continuous passage, al-

. though it has been found preferable to connect the upper or coolerportion of these tubes in such a way as to provide two parallel streamsof oil, which are then preferably merged into a single stream forpassage through the lower or hotter portion of this intermediatesection.

Many advantages arise from the handling of the oil in the mannerindicated above. A primary advantage is the lengthening of the life ofthe lowermost tubes of the coil, which are subjected to the most severeoutside temperature and are,.in accordance with this invention,subjected to a less severe inside temperature than is normally the case.Furthermore, the merging of the fresh charge and refluXed material priorto theirl passage through this lower section serves to lighten themixture which is passed through these tubes and thereby lessens thetendency to deposit carbon. By virtue of the arrangement of the tubes,partly in series and partly in parallel, the desired velocityof the oilis maintained through the 'hottest section of the coil while through thecooler sections where the liability to deposit carbon is less, a greatertime element is provided for the absorption of heat.

With the foregoing objects and advantages in View, one suitable form ofthe invention will now be described in greater detail with reference tothe accompanying drawings which form a part hereof and in which- Figure1 illustrates schematically the general arrangement of one suitable formof cracking system embodying the present invention, and

Figure 2 illustrates schematically the arrangement and form ofconnection between the several tubes constituting a preferred form ofthelieating coil.

l/Vhile one form of the invention, as applied to a cracking system, isdisclosed in this case, anda modiiied or preferred form of coil isshown, it is to be understood that this disclosure is merelyillustrative and that the invention is capable of applica-tion to avariety of other systems.

Referring now to Figure 1,--10 designates generally the entire heatingcoil consisting of three separate sections including an economizersection 11, an intermediate section 12, and a lower section 13, adaptedto receive the greatest intensity of heat from the burner 14. Oil whichhas been heated in the several sections of the coil 10 by passagetherethrough, in a lsequence which will be eX- plained hereinafter, isthen passed by means of a line 15 to one or more of a series or batteryof stills 16. In the form of apparatus illustrated, the heated oil maybe split into three separate streams which may be led into the firstthree of the battery of stills or drums, although by means of the valvesshown, this may be varied to suit the particular needs. The stills arepreferably interconnected, both above and below the liquid level line,and the vapors generated in all of them are 'adapted to be carried by apipe 17 to a suitable dephlegmator 4or fractionating tower 18. A portionof the vapors will be condensed in this tower and will collect in thebase, from which they may be withdrawn by means of a pump 19 andrecycled through the heating coil in a manner to be explained: thosevapors which persist as such through the tower are carried into arefluxing condenser 20 andfrom the latter, beyond to a final Condenserand suitable collecting apparatus. Within the condenser 2O there ispreferably located a coil 21 through which the incoming fresh charge ofoil is first passed in heat exchange relation with thevapors passingthrough this condenser. In this way the temperature of the fresh chargeis raised to a certain extent and at the same time a portion of thevapors are condensed and returned l'to the top of the vfractionatingtower by means of the backtrap line 22, to serve as a cooling andregulating medium therefor. If desired, a portion or all of the chargemaybe by-passed by a proper manipulation'of the valves shown.

From the coil 21 the fresh charge is passed by means of al pipe 23 toanother coil'24 which is mountedl Vin a container25. This container isin the path offlow ofthe-carry residues which will bewithdrawn from timevkto-time from the series of stills 16 through the pipes 26, so that asecond heatexchange is provided between these residues and the freshoil. Beyond the container, the residuum maybepassed through a suitablecooling tank 27 and on to any suitable storage tanks.

In its passage through the coil 24, the fresh charge of oil will haveitstemperature raised a second step above its initial temperature and itmay now be passed by means of a line 28 to the inlet end of theeconomizer section of the coil 10. After traversing the tubes of theeconomizer, the charge is passed by means of a line 29 to a point 30near the lower section of the heating coil-where it is merged with thecondensate which is being pumped by means of the pump 19 from the baseofthe fractionating tower. The mixture of fresh oil and returnedcondensate is then forced through a line 31 to the lowermost tubesforming section 13 of the coil, which is subjected to the highesttemperature within the furnace. As manytiers or rows of the tubes at thebottom of the coil'may be 'connected in series asdesired to form thelowermost and hottest section of the coil. After leaving the upper endof this section, the oil is passed through a line 32 intothe top of aseries of tubes forming the intermediate section 12 of the coil, fromthe lower end of which the heated mixture of fresh charge and condensateis passed, as before explained, by means of the line 15 into one or moreof the battery of stills 16.

In connection with the foregoing description, the heating coil has beenregarded as comprising, in all of its sections, a single passage throughwhich all of the oil is passed in series. If desired, the tubes which goto make -up the coil maybe soconnected as to provide a number ofparallel channels through which Y the oil may be passed. Figure i2discloses one suitable form of connection between the tubes for thispurpose to provide a relatively slow movement of the oil through theupper or economizer section, a very rapid flow of the oil through thelowermostor hottest section and different speeds of flow, Varying from arelatively slow speed to the maximum speed `throughthe intermediatesection. 1n this iioure, there is disclosed a furnace 33 in which thecoil is mounted and which is pro-y vided with any suitable form` ofburner 34 for supplying heat tothe tubes. Within the furnace there isarranged, to form the coil,

f a series of tubes 35 placed horizontally and in a plurality of rows.Any number of rows of these tubes may be selected to form the economizersection and in this section suitable headers 350 may be provided forjoining the staggered with relation to each other and the:

tubes of the-entire row-are thus divided into groups of three, v whichare lseries-connected and through which the yoil passes in threeparallel streams. F or the purposef of-vconducting the oil from an upperto ya lower row of tubes, a suitable header 36 may beprovided and thismay serve to join a group ofthree tubes in each of the two rowsl vIfdesired,

' there may be provided, in lieu of they header` 36, three indvidualreturn bends each connecting (one of the tubes of. an upperrow with oneofthe tubes of a neXt lower row;v

After the charge has'been made tofpass of tubes inthis manner, in anydesired number of? rows forming the economizer section, a header joiningthe last-three tubes lof the lowermost of the economizer rows 'may be in'three parallel streams through thel setsr* connected to a line 37which, at its lower end,

joins the pipe 31 at the juncture point 30 where the fresh charge andreturned condensate are merged. The pipe 31 will preferably be connectedonly to a single tube in the row' will be joined successively at one endto the next adjacent tube by means ofsuitable headers or return bends 38so as to form one continuous channel.l Several Vof the lowermost rows oftubes 'may be connectedy together n, by headers 39 to fornra singlecontinuous' lowermost row while each of the tubes of this I nected by apipe 40 to a header 400 joining a,

pair of tubes in the uppermost row of the intermedfiate section.Suitable headers 41 are then provided in thisrrowfor successivelyjoining one vvend of each pair of tubes to the next'adjoining pair so asto form two continuous lparallel channels for the oil and thisarrangement may be continued down through any desired number of rowsofvtubes. Headers 42 may be provided'to joinan end pair of `tubes in onerow with thecorresponding end pair of the next' lower row, or, ifdesired, the pairs of tubes in the'adjacent rows may be connected by apair of single headers or return bends.v After traversing a suit-l ableportion of the intermediate sect-ion of.

the coil in apair of-parallel streams, the oilt v will preferably bemerged intov a single stream by means of a suitable header 43 whichserves to connect the end pair of tubes in the lowermostl row of thisportionof the A. tubes with a. single end tube of afneX't lower" row. iSuitable headers or return bends 44 are then provided yin this rowftosuccessively join adjacent tubes of this row in series to130 forml onecontinuous passage. vA similar header 45 maybe providedto join .the endtubes of adjacent rows of this section of the coil so that any suitablenumber of rows of tubes may be employed in this relatively hot portionof the intermediate section. From one end of the lowermost row of tubesin this section, the oil is then passed into the pipe 15 leading to thebattery of stills 16.

In' the operation of the system which has been described, the conditionsas to temperature and pressure at the various stages may be variedwithinvery wide limits. `Suitable ranges may be mentioned here purelyfor the purpose of illustration and without any intention of limitingthe scope of the invention. As for pressure, it is contemplated aspreferable to maintain a substantially uni- :formv condition throughoutthe system to a point beyond the final condenser subject to such drops'as may be brought about by the frictionl in the various parts. Thispressure will preferably. range between 100 lbs. and 500 lbs., or evenhigher, in the coil and may drop from lbs. to 50 lbs. through thesystem. I-f desired, a substantial drop in pressure might well beprovided between the coil and the drum or series of drums and/or betweenthe drums and the fractionating apparatus. Suitable temperature rangesmight be such as to provide a charge to be introduced into theeconomizer coil at a vtemperature between 400 andy 550 F. and leavingthe economizer coil at between 500 and 7 00 F. The hottest section ofthe coil might well besubjected to temperatures between l200 Vand 1800F. and might serve to raise the has been disclosed herein, it is to beunderstood that it is capable of various modifications without departingfrom the spirit of the invention and it is desired to be limited'only inthis respect by the scope of the claims which follow:

What' I claim is:

1.- The methodpof cracking hydrocarbon oils which comprisesflowing theoil through the lowest temperature section of a heating' zoneina-plurality of streams in parallel, then passingthe heated oil in asingle stream through the hottest section of thek heating zone, thenpassino' the oil through an intermediate section of the heating zone ina plurality of streams in parallel, separately with.- drawing vaporousproducts and condensing the heavier constituents thereof, and return- Ying the resulting condensate to the stream of uniting the oil streamsinto a single stream and passing the said stream through a heatmg zoneofhigher temperature than that in the immediately preceding section oftheheatng Zone, separately withdrawing Vaporous products and condensingthe heavier constituents thereof, and returning the resulting condensateto the stream of oil flowing through the said hottest section of theheating zone. y

3. The method of cracking hydrocarbon oils which comprises flowing theoil through y the lowest temperature section of a heating zone in aplurality of streams in parallel, then passing the heated oil in asingle stream through a radiant heat section of the heating zone, thenpassing the oil through an intermediate section, separately withdrawingvaporcus products and condensing the heavier constituents thereof, andreturning the resulting condensate to the stream of oil flowing throughthe radiant heat section of the heating Zone.

4. The method of cracking hydrocarbonoils which comprises flowing theoil through a relatively low temperature heating zone in a plurality ofstreams in parallel, then passing the heated oil in a single streamthrough a radiant heat Zone, thereafter passing the oil through aheating Zone in a plurality of streams in parallel maintained at atemperature intermediate the temperature of the said first and secondnamed heating zones, separately withdrawing vaporous products and aplurality of streams in parallel, thereafterV condensing the heavierconstituents thereof,

and returning the resulting condensate tothe stream of oil flowingthrough the said radiant heat Zone.

5. The method of cracking hydrocarbon oils which comprises flowing theoil through a relatively low temperature heating Zone in a plurality ofstreams in parallel, then passing the heated oil-ina single streamthrough a relatively high temperature heating zone, thereafter passingthe oil in a plurality of streams in parallel, through a heating Zonemaintained at a temperature intermediate the temperature of the saidfirst and second named heating zones, separately withdrawing vaporousproducts and condensing the heavier constituents thereof, and returningthe resulting condensate to the stream of oil flowing through the saidhigh temperature zone.

6. The method of cracking hydrocarbon oils which comprises flowing theoil through a relatively W temperature heating zone in a plurality ofstreams in parallel, then passing the heated oil in a single streamthrough a relatively high temperature heating Zone,

Y thereafter passing the oil in a plurality of streams in parallelthrough a heating zone maintained at a temperature intermediate thetemperature of the said first and second named heating zones, thereafteruniting the streams into a single stream and passing the said streamthrough a heating zone of higher temperature than said third-namedheating zone and of lower temperature than said second-named heatingzone, separately Withdrawing vaporous products and condensing theheavier constituents thereof, and returning the resulting condensate tothe stream of oil flowing through the said high temperature zone.

In Witness whereof I have hereunto set my hand this 21st day of April,1928.

HORACE A. FOUTS.

